1. Field of the Invention
Embodiments of the present invention relate to an in vivo information acquiring apparatus that is introduced to an inner portion of a subject and acquires information on an inside of a body.
2. Description of the Related Art
In recent years, in the field of endoscopes, in vivo information acquiring apparatuses, which are swallow-type capsule endoscopes, have appeared. A capsule endoscope, which is swallowed from the mouth of a subject and thereby introduced to the inside of the body, has a function of moving inside body cavities, for example, organs such as the stomach and the small intestine according to peristaltic motion to sequentially pick up images until the capsule endoscope is naturally egested.
During the movement inside the body cavities, data of images picked up by the capsule endoscope inside the body is transmitted to the outside via wireless communication and accumulated in a memory provided inside an external receiver. After a patient swallows a capsule endoscope, the patient is free to do what he/she wants until the capsule endoscope is egested, carrying a receiver having the wireless communication function and the memory function with him/her.
A capsule endoscope obtains drive power from, e.g., a battery incorporated in its casing; however, it is impossible that a user performs an operation to turn on/off driving via, e.g., a switch disposed on an outer face of the casing because of its structure in which, e.g., an internal circuit is also sealed inside the casing. Therefore, capsule endoscopes including a switch inside their casings, the switch being turned on/off according to an external signal, have been proposed.
An in vivo observation system 101 disclosed in Japanese Patent Application Laid-Open Publication No. 2009-89907, which is illustrated in FIG. 1, includes a capsule endoscope 110, a transmission apparatus 102 that transmits an alternating magnetic field signal from the outside of the capsule endoscope 110, and a reception apparatus 103 that receives an image signal from the capsule endoscope 110.
The transmission apparatus 102 includes a power source 102A, a drive section 102B, and a transmission section 102C, which is a magnetic field generating section. The reception apparatus 103 includes an antenna unit 103C, an image receiving section 103B, and an external memory 103A that stores an image.
The capsule endoscope 110 includes a signal receiving section (hereinafter also referred to as “reception section”) 111, a control section 121, a battery 119, a switch 125, which is a P-channel FET, and an information acquiring section 126. The information acquiring section 126 includes an illumination unit 128 that emits illuminating light for illuminating an object inside a body, an image pickup unit 127 that picks up an image of the object illuminated by the illumination unit 128 and outputs the image as an image signal, and an RF unit 129 that wirelessly conveys the image signal outputted from the image pickup unit 127 to the outside of the body.
The reception section 111 includes a reception sensor 112 and a reception circuit 113. The reception sensor 112 includes a magnetic field detection coil 112A that outputs an alternating current signal having a magnitude according to a strength of an alternating magnetic field and a resonance capacitor 112B. The reception circuit 113 includes a diode 113A and a capacitor 113B that rectify the alternating current signal outputted from the reception sensor 112 and a resistance 113C.
An output signal S2 from a frequency dividing circuit 122 in the control section 121 is inverted via an output signal S1 from the reception section 111. The switch 125 includes a source connected to the battery 119, a gate connected to an output end of the frequency dividing circuit 122, and a drain connected to the information acquiring section 126.
In the capsule endoscope 110 having the above-described configuration, an alternating magnetic field signal from the signal transmission apparatus 102 is received by the magnetic field detection coil 112A, and based on an internal signal S2 resulting from the received signal being rectified and subjected to frequency division by two in the frequency dividing circuit 122, toggle between supply and stop of power to the information acquiring section 126 is controlled.